Octadecanol Research Articles

NiCo@EG-based composite PCMs with boosted thermal conductivity and photothermal conversion efficiency for solar energy harvesting

The application of phase change materials (PCMs) in solar energy is hampered by challenges such as insufficient photothermal conversion efficiency, low thermal conductivity and leakage. In this study, a novel composite PCMs based on NiCo@EG were prepared to solve the problems of low thermal conductivity, high leakage rate and inefficient photothermal performance. The NiCo@EG is obtained through calcination of the product of Ni-Co-BTC in-situ on expanded graphite (EG). In the composite PCMs, the octadecanol (OD) acts as a latent heat storage unit, the EG retains its porous network structure as an encapsulating skeleton. The nickel and cobalt nanoparticles derived from Ni-Co-BTC bimetallic organic frameworks are uniformly fixed on the surface of the EG, which could not only construct multiple thermal conduction pathways, but also enhance the photon-trapping ability. Benefiting from the synergy effect of nickel, cobalt metal nanoparticles and EG, the prepared OD/NiCo@EG-550 composite PCMs display high latent heat (168.3 J/g), excellent photothermal conversion efficiency (98.71 %), and improved thermal conductivity of 12.873 W/(m·K). Furthermore, the composite PCMs demonstrate exceptional shape stability, thermal stability, and robust thermal reliability. In summary, the high-efficiency photothermal composite PCMs display significant potential in improving the utilization of solar energy.

Multifunctional 1–octadecanol/expanded graphite/Fe3O4 composite phase change materials with effective solar–to–thermal and magnetic–to–thermal conversion and storage

Composite phase change materials (CPCMs) with multifunctional thermal conversion and storage abilities have demonstrated exceptional properties for diverse energy storage applications recently; however, these composite materials often encounter limitations of low heat storage capacity and high cost. In this study, novel 1–octadecanol (OD)/expanded graphite (EG)/Fe3O4 CPCMs were facilely prepared and characterized for multifunctional thermal conversion and storage properties. The composites showed excellent thermal energy storage capacities, reaching 185.5 J/g at 80 % OD accompanied by high crystallization fractions of above 95 %. In addition, they exhibited great thermal conductivities, excellent leakage resistance, thermal stability, and reliability. Under simulated solar irradiation, the prepared OD/EG/Fe3O4 CPCMs exhibited a rapid temperature increase from 34 to 70 °C, achieving solar–to–thermal conversion efficiency of 80.2–90.5 %. This behavior can be attributed to its ability to capture and convert photons into thermal energy, facilitated by the synergistic effects of the conjugated double–bond system of EG and localized surface plasmon resonance of Fe3O4 nanoparticles. Furthermore, the prepared OD/EG/Fe3O4 CPCMs exhibited superparamagnetic properties, accelerating their temperatures from 32 °C to 88 °C within 11–23 s when subjected to an alternating magnetic field. This demonstrates magnetic–to–thermal conversion and storage ability. These findings highlight the potential of OD/EG/Fe3O4 CPCMs as promising and cost–effective materials for various practical thermal storage applications.

Discoloration performance and mechanism research of a novel thermochromic energy storage material

The combination of phase change materials and thermochromic materials can realize the purpose of changing color while storing energy, so as to play the role of temperature regulation and color warning. In this paper, a thermochromic energy storage material (TESM) was prepared by using crystal violet lactone (CVL) and cresol red (CSR) as color former and color developer each other, taking octadecanol (OD) as the solvent and the energy storage material. The phase transition of OD induces ring-opened and ring-closed of lactone in both CVL and CSR, further leading to better discoloration. The influence of different proportions on the discoloration effect was studied. The thermal properties and functional groups of the samples were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and Fourier transform infrared spectrometer (FT-IR). The discoloration and re-coloration mechanism were explored. The results showed that the color of the prepared TESM can reversibly change between yellow-green (at room temperature) and red (at high temperature). The discoloration is attributed to the change of the intermolecular force between OD and CSR caused by the solid-liquid phase transformation of OD. When m(CVL): m(CSR): m(OD) = 3:1:500 (B3), the color difference of the prepared TESM is 38.81 NBS and the melting enthalpy is 219.8 J/g. Moreover, the prepared TESM shows good thermal stability and thermal cycling performance, and it has broad application prospects in the field of temperature alert and control.

Fe3O4/carbon-decorated graphene boosts photothermal conversion and storage of phase change materials

Pristine organic phase change materials (PCMs) are difficult to complete photothermal conversion and storage. To upgrade their photothermal conversion and storage capacity, we developed Fe-MOF (metal-organic framework) derived Fe3O4/C-decorated graphene (GP) based composite PCMs toward solar energy harvesting. Graphene is an excellent phonon conductor, and Fe3O4/C-GP as a photon capturer exhibits strong full-spectrum absorption. Additionally, Fe-MOF derived Fe3O4 nanoparticles are anchored on graphene nanosheets to reduce interfacial thermal resistance, shorten thermal diffusion path, and accelerate phonon transport. After the encapsulation of octadecanol (ODA) in Fe3O4/C-GP, ODA@Fe3O4/C-GP composite PCMs yield a high photothermal conversion efficiency of 88.18 % under 0.12 W/cm2 benefiting from the synergistic effect of 3D interconnected graphene framework and Fe3O4 nanoparticles with localized surface plasmon resonance effect. Moreover, ODA@Fe3O4/C-GP composite PCMs exhibit excellent latent heat storage stability, photothermal conversion stability and durable reliability after undergoing multiple cycle evaluation, boosting high-efficiency utilization of solar energy.

Formulation and phase change mechanism of Capric acid/Octadecanol binary composite phase change materials

Fatty acids and fatty alcohols have the advantages of high latent heat of phase change, good thermal stability, no corrosion, no supercooling and phase separation. They can be used as phase change energy storage materials for passive temperature control. However, their popularization and application are limited because of their high phase transition temperature and narrow phase transition range. This study develops a novel binary composite phase change materials (PCMs) of Capric acid (CA) and Octadecanol (OD) by a melt blending method. The theoretical calculation and hot melt-step cooling were carried out to generate an optimal molar ratio, followed by DSC thermal characterization. ATR-FTIR and XRD were performed to determine the phase transformation and chemical and structure changes. The results showed the binary CA-OD binary composite PCMs has a high latent heat of fusion, a melting temperature Tm = 26.48 °C and △H = 181.06 J/g at optimal mass ratio of 85.15:14.86 (CA:OD), which is higher than the theoretically predicted latent heat of phase transition, indicating a good synergistic effect beneficial to energy storage. Solid CA exists in the form of dimer and –OH in solid OD exists in form of association, and intermolecular hydrogen bonds weakens in liquid. There are hydrogen bonds in the CA-OD binary composite PCMs, and the molecular structure changes before and after the phase transformation were similar to that of a single component CA or OD. The crystal structures of the two compounds also change and the latent heat of phase transformation is improved. Finally, through TG and high and low temperature cycle test, CA-OD binary PCMs demonstrates good thermal stability and practicability in the field of building energy conservation.

Carbonized conjugated microporous polymers hollow spheres incorporated with fatty alcohols for ultra-highly efficient energy storage and conversion

With the increasing global instability in the development of the world, the efficient storage and conversion of energy have alerted attention. In this work, a novel conjugated microporous polymer hollow spheres (CMPHS) with a high specific surface (323 m2 g−1) and unique cavity structure are creatively prepared. By treatment with simple carbonization, the resulting carbonized microspheres (CCMPHS) show a high light absorption (80%) and outstanding thermal stability (thermal decomposition at 506 °C). On basis of the abundant micropores distributed on the surface of microspheres, the organic phase change materials (PCMs) i.e., fatty alcohols (tetradecanol (TD), hexadecanol (HD), and octadecanol (OD)), are successfully embedded into CCMPHS to afford a kind of new composite ([email protected]) for energy storage and conversion. The three kinds of [email protected] exhibit high latent heats (220.1 kJ kg−1, 244.6 kJ kg−1, and 228.8 kJ kg−1, respectively.). In terms of energy conversion, the photothermal conversion efficiencies of [email protected] are up to 86.83%, 89.45%, and 85.40% and the electrothermal conversion efficiencies are 83.81%, 81.10%, and 90.50%, which possess one of the highest values among the most of similar composites embed with PCMs reported to dates. Based on the advantages of simple fabrication, easy to scale up, high energy density, and conversion efficiency, the [email protected] are expected to be one of the most promising candidates as efficient PCMs composite for a variety of practical applications such as solar or electric energy harvesting, storage, conversion, and so on.

Photo- and magneto-responsive highly graphitized carbon based phase change composites for energy conversion and storage

Phase change material (PCM) as latent heat storage unit shows great potential in various scenes, including solar energy storage system and magnetically induced energy conversion and storage. But insufficient optical activity and electromagnetic response capability seriously hinder its wider applications. Herein, we reported an advanced high-performance photo- and magneto-driven composite phase change material (CPCM), where metal-organic framework (MOF) derived magnetic highly graphitized carbon (MGC) served as a fast-charging photo- and magneto-responsive supporting skeleton, and octadecanol (ODA) acted as a latent heat storage unit. In graphitic structure, there were numerous sp2 carbon atoms and π electrons. Under solar irradiation, heat is quickly discharged by lattice vibration resulting from π-π∗ transition and subsequent electron-phonon coupling in highly graphitized carbon. Moreover, in situ anchored magnetic cobalt nanoparticles contribute to another exothermic effect triggered by light and alternative magnetic field owing to its surface plasmon resonance (SPR) and eddy current effect, respectively. Additionally, cobalt nanoparticles can also serve as the heterogenous nucleation sites to promote the crystallinity of ODA molecules, thus profiting the increase of phase change enthalpy. Therefore, our developed cobalt-decorated highly graphitized carbon based photo- and magneto-responsive CPCM synergistically reached an enhanced photothermal efficiency of 88.1%, thermal energy storage capacity of 131.14 J/g, and excellent thermal cycling stability and reliability after undergoing multiple charging-discharging cycles, showing great potential in latent heat storage, solar and magnetic energy harvesting.

3D network structural shape-stabilized composite PCMs for integrated enhancement of thermal conductivity and photothermal properties

Metal organic frameworks (MOFs) are rarely used in the field of phase change heat storage, because their low thermal conductivity affects the practical application of composite phase change materials (PCMs). Three dimensional porous materials with good thermal conductivity and adsorption properties can be synthesized by cleverly combining high adsorption MOF with high thermal conductivity expanded graphite (EG). In this paper, ZIF-8 of zeolites with imidazole structure with high adsorption was prepared by method of co-precipitation. ZnO was prepared by carbonizing ZIF-8 in a vacuum tube furnace at 700°C. EG/[email protected] was synthesized by compounding EG, the crosslinking agent polyvinylpyrrolidone (PVP) and photothermal materials (CuS). Finally, OC/EG/[email protected] was prepared by stirring impregnation process according to four different proportions of octadecanol (OC) and compounding with EG/[email protected] The microstructure and thermal properties of the samples were characterized. The result shows that the enthalpy of composite phase change materials OC/EG/[email protected] reaches 202.97 J/g, which greatly improves the adsorption performance of OC and improves the heat storage performance. The thermal conductivity test results show that the thermal conductivity of the composite PCMs with the ratio of ZnO to EG (1:8) is as high as about 11.77 W/(m·K). The results of photothermal experiments show that the composite PCM with CuS can improve its photothermal properties.

Biomass-based phase change material gels demonstrating solar-thermal conversion and thermal energy storage for thermoelectric power generation and personal thermal management

The utilization of renewable biomass and the conversion of renewable energy are promising strategies for providing clean energy and meeting energy needs. In this work, a ternary phase change material gels (PCMGs) composed of octadecanol (OD), styrene-ethylene-butylene-styrene (SEBS) and hydroxylated carbon nanotubes (HCNTs) are proposed to realize the biomass utilization and solar energy harvesting. As a kind of biomass, OD possesses the characteristics of high phase change latent heat, low cost, renewability, environmental friendliness and biosafety. SEBS provides the crosslinked network to load the OD and introduce the free-standing feature. The HCNTs can realize the highly-efficient solar harvesting through the solar-thermal conversion. The Van der Waals force between SEBS and OD, the π-π interaction between SEBS and HCNTs and the hydrogen bond between OD and HCNTs enable the excellent form-stability. Taking advantages of the synergistic effect of the functional components, the proposed biomass-based PCMGs demonstrate high thermal energy storage capacity of 183.04 Jg−1, high solar absorbance of 95.68%, high cost-effectiveness of 3.92 × 10-5$J−1 and high cell viability of 117.9%. The biomass-based PCMGs are effectively applied in the thermoelectric power generation and personal thermal management. This work creates a state-of-the-art alternative for the next-generation solar-thermal materials devices.

CuO Nanoparticle@Polystyrene Hierarchical Porous Foam for the Effective Encapsulation of Octadecanol as a Phase Changing Thermal Energy Storage Material

CuO nanoparticle-doped hierarchical porous polymeric frameworks can be used for shape stability of octadecanol (OD) as a phase change material (PCM) for latent heat energy storage (LHTES) applications. A hierarchical porous foam polymer was synthesized by high internal phase emulsion polymerization of styrene and divinylbenzene doped with/without CuO. The synthesized high internal phase templated polymers (PHPs) with hierarchical pores were capable of absorbing up to 75 wt % OD without seepage behavior. The morphological, structural, and thermal behavior of PHPs/OD and PHPs@CuO/OD composite PCMs was determined using scanning electron microscopy (SEM)/energy-dispersive X-ray analysis (EDX), Brunauer–Emmett–Teller (BET) surface area analyses, Fourier transform infrared spectrophotometry (FT-IR), differential scanning calorimetry (DSC) analysis, and thermogravimetric analysis. Thermal analysis results revealed that PHP containing 75 wt % OD has an LHTES capacity of 190.4–194.0 J/g in the temperature range of 52.0–53.0 °C. The chemical and thermal stabilities of the developed composite PCMs were tested with repetitive thermal cycles. After 0.25 wt % CuO nanoparticle doping, the thermal conductivity of the composite PCM increased up to 86 and 17% compared to PHP and pure OD, respectively. Heat storage/releasing times of PHP@CuO/OD reduced about 20–22% relative to those of PHP/OD because of improved thermal conductivity. The thermal stability of PHP/OD and PHP@CuO/OD composites increased from 196 to 278 °C and 251 °C, respectively, compared to pure OD. The results exposed that especially PHP@CuO/OD composite PCMs are good candidates for LHTES applications because of their considerably high LHTES capacity.

Preparation and properties of lauric acid-octadecanol/expanded graphite shape-stabilized phase change energy storage material

In order to obtain sustainable phase change material (PCM) with excellent thermal properties for building energy conservation, a LA-OD binary eutectic system was designed and prepared by melt blending of lauric acid (LA) and octadecanol (OD). Phase transition temperature (PTT), latent heat (LH) and optimum ratio of LA-OD were determined by theory calculation, step cooling curve and differential scanning calorimetry (DSC) test. LA-OD and EG were combined into LA-OD/EG shape-stabilized phase change energy storage material (SSPCESM) by method of vacuum adsorption. The best ratio of EG to LA-OD is 1:9 under heat treatment experiments. In this case, the pores of EG are almost filled with LA-OD by scanning electron microscope (SEM), and the leakage of LA-OD is well controlled when the phase transition of LA-OD occurs. Thermal storage properties are determined by DSC, the melting point of SSPCESM with the LA-OD (90 wt%) is 36.06 °C, where the corresponding LH value of 176.44 J/g. The molecular characteristics and microstructure of the material were analyzed by Fourier transform infrared spectrometer (FT-IR), X-ray diffractometer (XRD), which show that the LA-OD/EG is formed by the physical interaction and no chemical reaction occurs. Heat storage and release time is shortened about 3.7 times compared with no EG, which indicates the thermal conductivity of LA-OD is greatly enhanced by EG. The LA-OD/EG has excellent thermal and chemical stability after 1000 thermal cycles. Moreover, it has good heat resistance when the temperature is less than 132.01 °C by TG test. Expanded graphite (EG) is considered as the adsorption carrier to enhance the thermal conductivity of LA-OD greatly, and to reduce leakage of PCM effectively.

Thermal characteristics of the multilayered structural MOF-EG/OC composite phase change material in thermal energy storage

At present, low heat storage capacity of organic phase change materials (PCMs) becomes a common problem, and the addition of matrix can contribute to its application in practical engineering. Mixing the porous expanded graphite (EG) with Co3O4 via carbonation of ZIF-67 uniformly, the composite materials PVP@Co3O4/EG were prepared by crosslinking the agent PVP (polyvinyl pyrrolidone), simultaneously the multilayer structure porous OC-PVP@Co3O4/EG composites were prepared by melt-blending method with octadecanol (OC). The thermophysical properties of the composite PCMs appeared the difference by adjusting the ratio of OC to Co3O4. The micromorphology, phase transition enthalpy and phase transition temperature of composite PCMs were determined by scanning electron microscope (SEM) and differential scanning calorimeter (DSC). The multilayer structure prepared by Co3O4 and EG is conducive to the effective transmission of phonons around the axial point, and achieves the goal of efficient heat transfer between PCMs and the external environment. The obtained OC-PVP@Co3O4/EG (Co3O4:EG = 1:8) PCMs exhibited excellent thermal conductivity (11.4 W∙m−1∙K−1), large phase change enthalpy (187.04 kJ∙kg−1). The infrared imaging verified that the infrared light intensity of two thermally conductive substrates (Co3O4:EG = 1:4, 1:8) in the exothermic stage was less than the ratio of Co3O4:EG is 1:4 and 1:8, which was in accordance with the results of the charging/discharging experiments.

Preparation and Energy Storage Properties of a Lauric acid/Octadecanol Eutectic Mixture.

A phase change material (PCM) has the characteristics of latent heat storage, controllable phase transition temperature (PTT), and chemical stability. It can naturally regulate the ambient temperature in a certain range and reduce the load of air conditioning operation. Therefore, it plays an important role in the field of energy-saving buildings, and the PTT of PCM is one of the decisive factors. In this paper, through analyzing PCM installed in solar buildings at various regions, a binary eutectic mixture (EM) was prepared from lauric acid (LA) and octadecanol (OD) by the method of mixed melting, and the PTT and enthalpy of the EM were 39.87 °C and 186.94 J/g, respectively. The PTT, latent heat, and EM ratio were determined by theoretical calculation, the step cooling curve, and DSC. FT-IR result shows that no chemical reaction occurs among the components of composites, and the molecular forces are uniform and stable. XRD results further proves that no other phases existed in the composites. Thermal cycles (500) and the TG test show that the EM has excellent thermal stability and heat resistance, which meets the engineering application. Due to the thermodynamic properties of the EM, it can be used in thermal cooling of electronic systems, building envelopes, and thermal storage in solar buildings to obtain a good energy-saving effect.

Anisotropy-functionalized cellulose-based phase change materials with reinforced solar-thermal energy conversion and storage capacity

Improving the thermal stability and energy storage density of phase change materials (PCMs) in thermal energy storage systems is a key task for their practical applications in industrial production. Whereas, limited by the inherently inferior heat transfer and unsatisfactory visible light response capability, PCMs exhibit extremely low thermal storage/release capability, inhibiting their developments. Herein, we constructed porous cellulose nanofibril (CNF)/silver nanowire (AgNW) hybrid supporting materials possessing the highly ordered structure and characteristically anisotropic thermal transmission capacity by directional freeze-drying, in order to encapsulate octadecanol (OCO) and octodecane (OCC) by vacuum impregnation method. Profited by the infrequently anisotropic structures and high thermal conductivity AgNWs, CNF/AgNW hybrid materials present dissimilar thermal transmission rates in the transverse and longitudinal directions. The close contact of AgNWs to CNFs allows the energy harvesting by solar-excited AgNWs to rapid transfer to CNFs, which increases the phonon propagation of the cellulosic material lattice and implements the improvement of the thermal transmission ability of the hybrid carriers. The obtained series of composite PCMs show an improved thermal conductivity (enhanced by 72.7%), and thermal enthalpy is comparatively approaching the theoretical value. Rejoicingly, the composites are thermally and durably stable. This novel-innovative targeted functional strategy provides insights into the thermal transmission mechanism in anisotropic supporting materials, and the resulting shape-stable composite PCMs (ss-CPCMs) can be employed as promising candidates for renewable thermal energy storage systems in virtue of their characteristic comprehensive performances.

A facile strategy of constructing composite form-stable phase change materials with superior high thermal conductivity using silicagel industrial wastes

The intrinsic poor thermal transport and liquid leakage of organic phase change materials (PCMs) greatly limit their applications in the field of solar thermal energy conversion and storage. Silica porous materials have usually been employed as supporting matrixes to incorporate PCMs and improve their thermal conductivities. However, the starting materials of synthesizing silica matrixes commonly involve high toxic chemical reagents. In this work, we have developed a facile strategy of constructing composite PCMs based on silicagel industrial wastes, in which paraffin wax (PW), myristic acid (MA) and octadecanol (OD) can be incorporated. Moreover, expanded graphite (EG) has been distributed into the PW composite PCMs to further enhance its thermal conductivity. The obtained composites behave stable form and excellent phase transition properties. The thermal conductivity of the PW composites can be achieved to be 5.87 W/(m·K), nearly 21.7 times higher than that of the pure PW. Furthermore, the 1000 melting-cooling cycle test indicates that the PW composites behave superior thermal cycle stability, exhibiting a promising long-term thermal energy storage application. This synthesis strategy may provide a promising way of low-cost preparation of form-stable composite PCMs with high thermal conductivity for solar thermal energy management and utilization.

Thermal energy storage and thermal conductivity properties of Octadecanol-MWCNT composite PCMs as promising organic heat storage materials

Fatty alcohols have been identified as promising organic phase change materials (PCMs) for thermal energy storage, because of their suitable temperature range, nontoxicity and can be obtained from both natural and synthetic sources. Like all other organic PCMs, octadecanol (OD) as PCM suffers from low thermal conductivity (TC). In this work, to enhance its TC, it was grafted on the functionalized MWCNT and were used as a conductive filler to enhance overall thermal properties of OD in a composite PCM (CPCMs) structure. The OD/OD-g-MWCNT sample showed better dispersion within the composites and the presence of additional OD boosted the overall heat storage enthalpy compared to that of plane composite sample with OD/MWCNT. In a non-quantitative approach, it was observed that, any increase in grafting ratio of OD increases the heat storage enthalpy of the composites. The heat storage enthalpy of (267.7 J/g) OD/OD-g-MWCNT(4:1)-5wt% composite PCM had reached very close to the heat storage enthalpy value of pure OD (269.3 J/g), and much higher than that of OD/MWCNT-5wt% (234.5 J/g). Champion sample i.e. OD/OD-g-MWCNT (4:1)-5wt%, showed good heat storage enthalpy, cycling performance, thermal stability and TC enhancement by 262.5%.

Effect of Surface Cleaning on Performance of Organic Friction Modifiers

The performance of surface-active additives, such as friction modifiers, depends on their interactions with surfaces. Their effectiveness thus hinges upon the surface conditions. In this work, the effect of cleaning methods of test substrates on the friction reduction capabilities of different organic friction modifier (OFM) additives was investigated. 52100 steel discs and balls were the test specimens. They were cleaned in five different ways. The cleaned surfaces were characterized by using ellipsometry and atomic force microscopy. The tribological performance of stearic acid (STA), octadecylamine (ODA), and octadecanol (ODO), on these surfaces was then tested.As-received steel surfaces were covered with contaminants that may impede the formation of an OFM surface layer. Cleaning these surfaces with solvents cannot completely remove these contaminants. Cleaning with oxygen or argon plasma results in cleaner surfaces compared to those cleaned by solvents only. The impact of the choice of cleaning method on friction depends on the strength of the interaction between the OFM and the steel surface, which determines the ability of an OFM to displace surface contaminations. Cleaner surfaces result in lower initial friction for STA and ODA. Steady-state friction is also affected but to a lesser extent. This may be because most contaminants that remained in the wear track were mechanically removed during rubbing.

Enhancements in cure rate index and mechanical properties of silica-filled natural rubber using octadecanol-fatty alcohol

The enhancements in cure rate index and mechanical/tensile properties of natural rubber (NR) filled with silica because of the addition of octadecanol (OCD)-fatty alcohol (FA) were investigated. The silica as a reinforcing filler was compounded into the NR at a fixed loading, 30 parts per hundred rubber (phr.). The OCD-FA was derived from the oil of palm kernel and compounded into the NR as an additive agent. The loading variations of OCD-FA were 0 to 4 phr. It was found that the OCD-FA functioned as a curative and plasticizing agent for the silica-filled NR compounds. As a co-curing agent, the OCD-FA enhanced the time of scorches and cure rate index-CRI of the compounds of NR. A higher the OCD-FA loading caused in a higher CRI degree. As a plasticizing agent, the OCD-FA decreased tensile moduli but increased elongation at break. It was also found that the OCD-FA increased both tensile strength and abrasion resistance of the compounds of NR up to a 2 phr. of loading. The addition of OCD-FA with a 2 phr. of was an optimum loading for the compounds of NR.

Effect of covalent functionalization and phase change matrix on heat transfer across graphene/phase change material interfaces

Owing to the superior thermal conductivity (TC) of graphene, graphene/phase change material (G/PCM) have the potential as the thermal interface materials (TIMs) dissipating heat for electronic packages. In this paper, the effect of three functional groups, i.e., hydroxyl (OH), carboxyl (COOH), butyl (C4H9) relative to pristine graphene (PG) and three PCM matrices, i.e., octadecane (OD), octadecanol (OA), stearic acid (SA), on the interfacial heat transfer between the PCM matrix and graphene was investigated by using molecular dynamic simulations. The simulation results show that the longer the chain of the covalent group, the stronger the van der Waals force will be, which will further enhance the interfacial coupling, and finally decrease the interface thermal resistance (ITR). For different PCM matrices, G/SA has the best heat transfer performance, followed by G/OA, and finally G/OD. The ITR of PG-OH/SA and PG-COOH/OA is remarkably reduced because the hydrogen bond formed by electrostatic attraction enhances the interfacial coupling. Additionally, based on the obtained ITR results and the effective medium theory, TC of G/PCM was studied. It was found that TC of PG/PCM increased as the volume fraction of the filler increased, and TC of PG/SA was always the largest, followed by PG/OA, and the smallest was PG/OD. At a filler volume fraction of 9%, PG-C4H9/PCM has the highest TC, followed by PG-COOH/PCM and PG-OH/PCM, and the smallest is PG/PCM. For different phase change matrices, TC of G/SA is generally the highest, followed by G/OA, and the lowest is G/OD. The high TC of PG-OH/SA and PG-COOH/OA is also due to enhanced interfacial coupling by hydrogen bonding.

Experimental investigation on thermal properties and thermal performance enhancement of octadecanol/expanded perlite form stable phase change materials for efficient thermal energy storage

Abstract Octadecanol (OC) was employed as phase change material (PCM) to compound with expanded perlite (EP) because of its relatively high latent heat capacity (245.97 kJ/kg). OC/EP composites were prepared via vacuum impregnation method in this paper. The microstructure, chemical components and interactions that between two materials were characterized via Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The leakage-proof properties of OC within the composites were investigated and the leakage phenomena were weakened by adding expanded graphite (EG) with mass fractions of 5%, 10% and 15%. The mass fraction of OC maintains 60% without any leakage after adding EG (mass fraction of 15%). Latent heat capacity and phase change temperature were tested via Differential Scanning Calorimeter (DSC). Latent heat capacity of 60% OC/EP/15EG is 140.20 kJ/kg, and phase change temperature is 59.00 °C. The thermal conductivity of the composites was tested, and the variation tendency was linearly fitted. The thermal storage and release tests were performed to evaluate thermal performance of the composites. And the efficiency of the heat storage and release of OC/EP composites were improved significantly after filling EG (mass fraction of 15%) into the interspace that is among the particles of EP.